The Effect of Upright Posture on Endothelial Function in Women and Men

We investigated flow-mediated dilation (FMD) and reactive hyperemia peripheral arterial tonometry (RH-PAT) responses during the supine and 70 head-up tilt postures to assess vascular function in young healthy women and men. During the FMD protocol: 1) FMD increased in both sexes during tilt (P=0.005), 2) women had higher shear stress responses in both postures vs. men (P=0.03), 3) at the time of maximal vasodilation during tilt, both sexes had lower mean arterial pressure responses (MAP; P=0.02) compared to supine. During the RH-PAT protocol: 1) at all timepoints men had greater RH-PAT in comparison to women (P=0.035), 2) both sexes had similar arterial stiffness in both postures (P>0.05), and 3) at the time of maximal vasodilation, both sexes showed similar MAP responses across both postures (P>0.05). We suggest that the increased vasodilatory response as measured by FMD in the tilt posture could be attributed to increasing metabolite production from postural muscles.